Rolling mills of this type are for example required in the production of aluminum sheet. Here, the sheet is produced during a procedure including several steps where first the billet is hot rolled. Once the billet has been rolled out sufficiently and, optionally, has been thermally treated, a cold rolling of the sheet is done to obtain its final thickness. Hot-rolling mills as well as cold-rolling mills are commonly used for this purpose and described in a sufficient manner in the state of the art.
WO 98/53111 (US 2002/0062889) discloses a method for producing hot rolled aluminum strips for cans, the method being intended to be particularly suitable for smaller production runs of less than 250,000 t per year. First, a back- and forth prerolling of the raw material is done in a hot-rolling mill, followed directly by the final rolling of the strip and subsequently by a thermal treatment of the strip that is wound into coils. Here, during the last of the final reduction passes, recrystallization in the roll material is suppressed by a regulated temperature control of the hot strip and the recrystallization is intended and allowed to happen only directly after the final rolling outside the rolling train.
WO 96/10655 (U.S. Pat. No. 5,362,341) and WO 96/10656 also relate to a method of producing aluminum sheets. Also in this case, a hot rolling of the billet or of the strip produced by the rolling process on the hot-rolling mill is done first. Then, a thermal treatment process is carried out and finally, a cold-rolling procedure is done in a cold-rolling mill.
The hot-rolling mill and the cold-rolling mill are fundamentally different from each other since the hot-rolling mill requires a conveyor for the material to be rolled extending on both sides of the roll stand over a predetermined length. First, the billet is introduced into the rolling mill and rolled out. Here, there is typically a back-and-forth process, i.e. the billet that becomes thinner and thinner from being rolled rolling moves back and forth through the roll stand. Once the hot-rolling procedure has been completed, the strip that is rolled out is wound onto a spool in order to form a coil.
In cold rolling, however, the already prepared coil is inserted into the rolling mill. The roll stand is located between two spools. The strip is wound off the coil of the spool and directed towards the roll nip. On the other side, the cold-rolled strip is fed to the other spool and rewound into a coil.
Due to these facts, the proportions or the installation space required are substantially different for a hot-rolling mill on the one hand, and a cold-rolling mill on the other hand. The hot-rolling mill is quite long, whereas the cold-rolling mill is relatively short.
In view of the efficiency of existing rolling mills and thus with respect to the economic efficiency of the investments, it is disadvantageous that a separate rolling mill is required for each process. This is in particular true if the hot-rolling mill is not required during the cold-rolling procedure and vice versa.